The present invention relates to an improved stepping motor for driving the hands of an electronic clock, and, more especially, to a stepping motor which produces a relatively large torque and in which there is no need to adjust the stators surrounding the rotor to determine the direction of the rotor's rotation.
The stepping motor in a conventional electronic clock is generally driven by periodic positive and negative electric signals of a square or a rectangular wave with a duty cycle of 50% to drive the stepping motor in the predetermined constant direction, where the electric signal is provided by an electronic circuit essentially composed of a crystal oscillator, a frequency divider, and an amplifier.
In order to greatly reduce the average current consumption of an electronic clock, it is also known to drive a stepping motor by a square wave with a smaller duty cycle than 50% or a pulse current having a changing and discharging characteristics.
These driving signals are, however, insufficient to provide a stepping motor with sufficiently high efficiency such that the average current consumption is reduced and, further, the torque from the stepping motor is increased in a stable manner.
Further, it is necessary in a conventional stepping motor for an electronic clock to adjust the stator of the motor to determine the direction of the motor's rotation, and to laminate iron cores of different formation to form the stator, which results in complex motor assembly, an inaccurate stepping angle for the motor, and a reduction of the stepping motor torque.